The postulated mechanism by which luteinizing hormone releasing hormone (LHRH) stimulates the release of gonadotropins is currently a topic of considerable controversy. Cyclic nucleotides are no longer thought to be the primary "second messenger" of LHRH. The goal of this project is to investigate the role of an alternate "second messenger", Ca++, in the action of LHRH. Populations of dispersed anterior pituitary cells as well as populations of enriched gonadotrophs will be used to characterize the pattern of LHRH-stimulated LH and FSH release. Within the framework of this pattern of LH release, the movements of Ca++ into and out of the cells during stimulation of LHRH will be investigated. The distribution of Ca++ within the cell during resting and active secretion will be studied using both radioactive 45Ca++ and fluorescent techniques. The influence of LHRH on both secretion and cytoplasmic levels of cyclic nucleotides will also be examined. Finally, we propose to investigate the LHRH-stimulation of membrane phospholipid turnover especially in reference to Ca++ fluxes.